Neonatal incubators create a micro environment that is thermally neutral where a neonate can develop. These incubators typically include a humidifier and associated control system that controls the humidity in the neonatal microenvironment. The humidifier comprises a device that evaporates an evaporant, such as distilled water, to increase relative humidity of air within the neonatal microenvironment. Such humidifiers typically have an evaporant source in the form of a reservoir that holds evaporant to be dispersed into the microenvironment within the incubator. For example, the humidifier may be an evaporative humidifier in which air is passed through a screen, wick, or other evaporate carrier to pick up moisture. In another embodiment, the humidifier may be a steam humidifier or vaporizer in which water is heated to cause evaporation. In yet another implementation, the humidifier comprises an impeller in which a rotating disk propels water at a cone-like diffuser to break the water into tiny droplets that float in the air. The humidifier is adjustable and controllable such that the rate at which water or water vapor is added to the microenvironment may be adjusted in order to control the humidity to a desired value.